Omnidirectional light beacon with toroidal flash lamp

ABSTRACT

A toroidal, gas filled arc discharge flash lamp encircles a reflector having a surface of revolution coaxial with the lamp and comprising the locus of normals to the bisectors of lines tangent to consistent loci on the toroidal lamp and of lines intersecting the axis at a constant angle. Light is reflected substantially uniformly nearly 360* around the reflector and concentrated around an angle somewhat above the horizontal.

United States Patent 1191 Levin Dec. 3, 1974 54 ()MNIDIRECTIONAL LI TBEACON 1,799,341 4/1931 Wiegand 240/12 1,939,345 12/1933 061111 et al240/12 ux WITH TOROIDAL FLASH LAMP 3,474,406 10/1909 0115m 240/12 x [75]Inventor: Robert E. Levin, South Hamilton,

Mass.

[73] Assignee: GTE Sylvania Incorporated,

Danvers, Mass.

[22] Filed: Dec. 22, 1972 [211 App]. No.: 317,791

[52] US. Cl. 240/4135 R, 240/12, 240/103 R [51] Int. Cl. F21v 7/00 [58]Field of Search 240/12, 41.35 R, 41.35 F,

[56] References Cited UNITED STATES PATENTS 1,120,219 12/1914 Mudge240/103R Primary ExaminerFred L. Braun Attorney, Agent, or Firm-James H.Grover [57] ABSTRACT A toroidal, gas filled arc discharge flash lampencircles a reflector having a surface of revolution coaxial with thelamp and comprising the locus of normals to the bisectors of linestangent to consistent loci on the toroidal lamp and of linesintersecting the axis at a constant angle. Light is reflectedsubstantially uniformly nearly 360 around the reflector and concentratedaround an angle somewhat above the horizontal.

1 Claim, 4 Drawing Figures PATENTEL DEB 3 I974 ANGLE ABOVE HORIZONTALFIG.3

FIG. 2

BACKGROUND OF THE INVENTION As disclosed in copending US. Pat.application Ser. No. 212,190, filed Dec. 21, 1971, now Pat. No.3,771,120 by Robert P. Bonazoli and Donald I. Coggins and erntitledAirport Runway Approach and Reference Lighting System and airport beaconunit may have both a directional gas discharge flash lamp and anomnidirectional flash lamp. The directional lamp or a series of them areaimed in a relatively narrow beam toward and on the correct line ofaircraft approaching a runway. The intensity of the lamp is governed bythe duration of its discharge. The omnidirectional lamp radiating in alldirections serves for earlier location of the runway,- and also servesas a quench tube for terminating discharge of the directional lamp,thereby controlling the intensity of the directional lamp lightemission.

The object of the present invention is to provide an improved opticalsystem for multidirectionally radiating light from the quench tube so asto produce a light intensity of nearly uniform magnitude insubstantially all directions about. a vertical axis, with maximumintensity at a preselected angle relative to the horizontal plane.

SUMMARY OF THE INVENTION According to the invention a multidirectionallight comprisees a lamp of toroidal volume curved in a planesubstantially around an axis normal to the plane, a reflector, and meansto mount the lamp in fixed relation thereto, the reflector comprising asurface of revolution curved around the lamp axis and defined by ageneratrix of the surface intersecting the lamp plane between the lampand its axis and comprising the locus of normals to bisectors of theangle between two sets of lines, the first lines being tangent toconsistent loci on the toroidal volume and-the second lines intersectingthe axis at a constant'angle such that the maximum in tensity ofreflected light is substantially uniform holder 12 electricallyinterconnects the lamp terminals with a power supply within the controlcabinet 1.

. FIG. 2

The reflector 4 is a polished, surface of revolution about the axis A ofa generatrixcurve G defined as follows. A portion of the lamp. 9 isshown in vertical section centered on the horizontal plane P anddisplaced outwardly a distance D from the axis of revolution and of thetoroidal lamp volume. A first line T is drawn tangent to the inwardsurface of the toroidal volume of the lamp 9. A second line Xintersecting the first line T at point 20 is drawn at the angle to thehorizontal plane P at which the lowest light ray 21 is desired toradiate from the reflector. In an airport beacon system it is usuallydesirable for the lowermost ray 21 to issue horizontally, parallel withthe ground, hence the line X is parallel, or at a zero degree angle tothe plane P. Where, as shown in FIG. 3, it is desired that the lowermostray 21* issue below the horizontal, the line X* is drawn at acorresponding angle x* to the horizontal. After drawing a bisector B ofthe angle between the first and secthrough', and concentrated around aselected-angle rel- FIG. 1-

As shown in FIG. 1 an omnidirectional flash lamp system suitable for usein the previously described airport system or for other beacon use ismounted on a control cabinet 1. The beacon comprises a base 2 attachinga clear or tinted transparent cylindrical glass enclosure 3 to the base2. Mounted on the base 2 is a hollow metallic reflector 4 having top andbottom portions 6 and 7 separably joined at a central seam 8. A flashlamp 9 of toroidal volume encircles the reflector in the plane of thecentral seam and with the lamp axis coincident with the reflector axisA. Brackets l l on the lower reflector portion 7 support. the lamp, anda lamp 0nd lines T and X, a line N normal (i.e., perpendicular) to thebisector B at the point P represents a reflecting increment on thegeneratrix G. Repetition of the development of the above describedincrement willtrac e the complete generatrix G. Successive first linesmust be drawn consistently tangent to successively adjacent surfaces ofthe lamp volume. To construct a particular generatrix curve a point onthe line P representing the horizontal plane is selected with regard tothe cross sectional radius R of the lamp volume-and to the radius of itstorus which equals the displacement D of the torus from the verticalaxis. Fora lamp of sectional radius R=0.6O cm. and toroidal diameterD=5.08 cm. a suitable value for the length of the first X1 from the axisA to the generatrix G is 3.11 cm. Other suitable dimensions shown inFIG. 2 are S=9.54 cm., U=ll.30.cm.,

W=.7.76 cm. These three latter dimensions are selected with respect tothe desiredlimits of the reflector size and the intensity ofconcentration; of the emitted light close to the horizontal or groundplane. For greater concentration the extreme upper and lower edges ofthe reflector are at a greater distance D+S from the axis A than thelamp displacement D, so that one or both of the extreme edges overhangthe lamp.

Having located one point on the generatrix curve a line T1 is drawn fromthe lamp volume, a bisecting line B drawn and a normal N to B drawn atthe selected point as described above with respect to point 20. Thegeneratrix curve is then completed graphically by connecting successivenormal increments to the first normal increment in a known constructionmanner.

The above graphic description of the generatrix is summarized asfollows: i

The generatrix G is the locus of normals N to bisectors B of the anglebetween first lines T tangent to the toroidal lamp volume and secondlines X intersecting the axis A of revolution at a constant angle x.

An equivalent description of a generatrix reflector may also be mademathematically in spherical coordinates p, g and r shown in FIG. 2according to the equation below wherein p is the angle in the verticalplane, 3 the angle in the horizontal planes,-r the variable'radius, Rthe fixed radius of the toroidal lamp volume, D the displacement of thelamp volume center C fromthe vertex V of the reflector, and H aparameter dependent on reflector size:

As shown in FIG. 2 by way of example, the dimensions of the reflector inrelation to the toroidal lamp may be 'as follows:

D 5.08 cm.

R 0.60 cm. S 9.54 cm.

U 11.30 cm.

W 7.76 cm.

. Either of the above graphic or mathematical methods will generate afamily of reflector curves, all of which satisfy the requirement thatthe lowermost ray issue from the reflector at the desired minimum anglewith respect to the horizontal plane P. Moreover the reflectors sogenerated will concentrate the beam of rays within a relatively narrowvertical angle above the lowermost ray. Although rays on lines 21consistently tangent to the inward surface of the lamp volume reflect atthe desired minimum angle x, rays such as 22 or 23 in FIG. 2 emanatingfrom outer surfaces of the toroidal volume will be reflected at an angle1 above, the horizontal. The'angle, however is limited and substantiallyall concentrated near the horizontal as shown in FIG. 4.

FIG. 4

A beacon constructed with the above dimensions will distribute lightwith the specific distribution shown by the solid line curve I. At thebelow zero degrees above the horizontal the intensity of radiation islow and dropping sharply. Maximum intensity is at about abovehorizontal, and above 5 drops off sharply, indicating the efficiency ofthe present reflector in concentrating light near the horizontal orother desired angle. Similarly the broken line curve I* shows a similarconcen- It should be understood that the present disclosure is for thepurpose of illustration only and that this invention includes allmodifications and equivalents which fall within the scope of theappended claims.

I claim: 1. A multidirectional light comprising: a lamp of toroidalvolume having an axis concentric with the toroidal volume and having itscentral plane intersected perpendicularly by the lamp axis, the lampbeing curved substantially around and equidistant from the lamp axis, areflector encircled by' the lamp with reflecting surfaces'extendingsubstantially above and below the central plane of the lamp, and meansto mount the lamp in fixed relation thereto, the reflector comprising acontinuous surface of rev olution curved around the lamp axis anddefined by a generatrix of the surface intersecting the central plane ofthe lamp between the lamp and its axis, wherein the generatrix isdefined by the equation:

wherein p is the angle to a given locus on the generatrix in thevertical plane, r the variable radius to the locus, R the fixed radiusof the torodial lamp volume, D the displacement of the lamp volumecenter in the central plane of the lamp from the vertex of thereflector, and H a parameter dependent on reflector size, the centralplane of the lamp being vertically asymmetric with respect to the vertexof the reflector so as to produce an asymmetric reflected lightdistribution pattern with a peak intensity close to and above thelowermost ray issuing from the reflector.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 852 584Dated December 3 1974 Inventor(s) Robert vin It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

In column 4, claim 1, at the end of line 23, that portion of theequation reading 2 cos2] should read cos In column 4, claim 1, line 24,that portion of the equation reading p2Dp should read 2Dp Signed andsealed this 18th day of March 1.975.

(SEAL) Attest:

C. IIARSHALL DANE RUTH C. EKSON Commissioner of Patents Attesting fficerand Trademarks ORM PO-1050 (10-69) USCOMM-DC 6O376-P69 U.S. GOVERNMENTPRINTING OFFICE ISQ 0366-334

1. A multidirectional light comprising: a lamp of toroidal volume havingan axis concentric with the toroidal volume and having its central planeintersected perpendicularly by the lamp axis, the lamp being curvedsubstantially around and equidistant from the lamp axis, a reflectorencircled by the lamp with reflecting surfaces extending substantiallyabove and below the central plane of the lamp, and means to mount thelamp in fixed relation thereto, the reflector comprising a continuoussurface of revolution curved around the lamp axis and defined by ageneratrix of the surface intersecting the central plane of the lampbetween the lamp and its axis, wherein the generatrix is defined by theequation: (r2-2Dr cos p + D2-R2)1/2 -R tan 1((r2-2Dr cos p + D2-R2)1/2/R) + R tan 1 (r sin p / (r2 cos2 p-p2Dp cos p + D2)1/2) -(r2 cos2 p -2Dr cos p + D2)1/2 - 2H 0 wherein p is the angle to a given locus on thegeneratrix in the vertical plane, r the variable radius to the locus, Rthe fixed radius of the torodial lamp volume, D the displacement of thelamp volume center in the central plane of the lamp from the vertex ofthe reflector, and H a parameter dependent on reflector size, thecentral plane of the lamp being vertically asymmetric with respect tothe vertex of the reflector so as to produce an asymmetric reflectedlight distribution pattern with a peak intensity close to and above thelowermost ray issuing from the reflector.